Certain electric systems include electric machines, such as electrical motors, that can create significant amounts of electrical noise, which can adversely affect other, more sensitive components. In order to reduce this electrical noise, filters are often added to these systems. And, the placement of such filters within the system is an important factor to the effectiveness of electrical noise reduction. For example, in an system with an electrical motor, it may be preferable to place the filter close to the point where the lead wires exit the motor housing.
Many systems include standardized electric motors that have electrical connectors. Such electrical connectors allow these motors to be more easily “plugged-in” to the system. In this way, systems with electrical motors can be more easily designed using readily-available, modular components, and those modular components can be more readily replaced, using the removable electrical connectors, should the need arise.
As previously stated, it is often desirable to include a noise filter when an electric motor is used in a system. Where the electric motor has a modular design with a removable electrical connector, it is convenient to include the filter as part of the motor module. Considering the design goal of locating the filter closer to the lead wires and/or electrical connector, previous motor designs have included the filter within the electrical connector.
While the components of many systems are subjected to significant stresses, electrical connectors are uniquely susceptible due to the non-permanent nature of their connection to a mating connector. Furthermore, the act of forming and breaking the mating connections creates additional stresses that electrical connectors must be able to withstand.
Previous attempts at integrating filters in connectors have used rigid printed circuit boards and/or overmolding. Overmolding is an injection molding process where one material (usually an elastromeric material) is molded “over” a secondary, rigid substrate material (such as a rigid printed circuit board).
The rigid printed circuit board and overmolding techniques were seen to be advantageous for electrical connectors because rigid bodies may be able to withstand environmental stresses while maintaining a consistent electrical connection in a system. For example, some electrical connectors are used with sensors in close proximity to an engine's combustion chambers. Previous electrical connector designs have utilized rigid components, such as rigid printed circuit boards (“PCBs”) to reduce and withstand mechanical and physical stresses, shock, vibration, and various thermal conditions.
However, the use of overmolding has shortcomings. First, the overmolding process is costly and time consuming as it requires two sequential molds. Furthermore, during the overmolding process, the substrate material must be stationary. Otherwise, it is difficult to repeatedly overmold substrates with a consistent outcome. As such, when overmolding flexible components, additional measures must be taken to ensure that the substrate does not move during the overmolding process. These additional measures increase the complexity, and therefore, the cost to produce electrical connectors. Also, filters can be bulky and susceptible to damage, especially if exposed to high-temperature assembly techniques such as overmolding.
Rigid components, such as PCBs, can be difficult to design into small form-factor housings (e.g., electrical connectors). There is generally a trade-off between the ability of a rigid component to fit into a small space and the ability of that component to be easily assembled. This trade-off creates a more costly and/or complex device.
Therefore, it is difficult to place filters in close proximity to the electrical connector and/or lead wires without increasing the cost and complexity of the connector.